Mobile (high-voltage) testers of the type mentioned in the introduction are adequately known from the prior art and are used for what is known as “very low frequency” (VLF) testing of measurement objects, which may be the most diverse electrical or electronic components or in particular high-voltage or medium-voltage cables. With VLF testing, the measurement object is subjected to a usually sinusoidal a.c. voltage with an rms voltage in the kV range and—by determination and evaluation of the test voltage present at the measurement object and of the test current caused hereby—information is obtained as to whether the tested measurement object has withstood the test voltage without voltage breakdown for a specified period. In the case of successive increases of the test voltage, it is then also possible to determine, for example, the test voltage at which voltage breakdowns relevant to safety first occur or have occurred.
Furthermore, with specially configured VLF testers of the aforesaid type, in conjunction with evaluation of the exact phase shift between test voltage and test current, it is also possible to determine the so-called loss factor (tan δ) of the measurement object and to use the results to estimate, for example, the quality or aging condition of the insulation of high-voltage or medium-voltage cables by means of a nondestructive test. The measurement and evaluation algorithms to be applied in this respect (and the measuring and evaluating circuits necessary for them) are adequately known to the person skilled in the pertinent art.
Particularly in the case of VLF testing of high-voltage or medium-voltage cables, the requirements imposed on the electrical power to be applied by VLF testers of the class in question become especially strict with increasing length of the cable to be tested, and the costs of mobile testers of the class in question rise rapidly with increasing output power. In practice, therefore, mobile testers of the type mentioned in the introduction are offered in various power classes, the service capabilities of which—depending on the voltage amplitudes that can be generated with the tester in question and on the output power available as a result—are limited. At present, mobile VLF testers with means for generating a sinusoidal VLF test voltage in a range of up to 200 kV peak voltage (corresponding to approximately 141 kV rms voltage) are available with electrical output powers of up to approximately 8 kW.
In view of the prior art mentioned in the foregoing, the object is to improve a VLF tester as well as a system and a method of the type mentioned in the introduction to provide additional value for the user in the functional respect.